Do u heat the bottles up for your babe?

I’m still TTC, but I’ve ALWAYS thought people warmed up their babies bottles so they have warm comforting formula/breast milk, every time. All my friends and cousins have babies and I’m noticing more and more that they don’t warm their babies bottles up. They use room temp water to make the bottles. And so many times I have seen my SIL take the bottle from the fridge and give it to her 3 month old🤯... I’m just trying to figure out if warming bottles up is still a thing anymore, do the pediatricians say it’s okay either way? I always thought they slept better and tolerated the milk better when it was warm 🤷🏼‍♀️

TIA ladies 😊